RINNAI (RUCS75I) REU-KCM2528FFU-US vs Ruud RTGH-84DVLN-3: which uses less energy?
At the high draw pattern the Ruud RTGH-84DVLN-3 uses 182 therms a year and the RINNAI (RUCS75I) REU-KCM2528FFU-US 188 — 6 therms (3%) less, about 61 therms over ten years. Both are filed as a gas tankless unit, so the comparison holds. Enter your ZIP below to price the difference.
Side by side
Compared within one class only: models filed as a gas tankless unit at the high draw pattern.
| Figure | RINNAI (RUCS75I) REU-KCM2528FFU-US | Ruud RTGH-84DVLN-3 |
|---|---|---|
| UEF (Uniform Energy Factor) | 0.9 | 0.93 (better) |
| Energy use per year (therms) | 188 | 182 (better) |
| Max flow (GPM) | 4.5 | 4.5 |
| Installed cost range | $2,122–$3,129 | $2,264–$3,294 |
| ENERGY STAR certified | not matched | not matched |
What it costs to run
Reliability
Not published: Reliability, failure rates and each model’s actual warranty term.
The registries these figures come from certify energy performance under a federal test; none of them records how long a unit lasts or how often it fails, so this page does not rank the two on reliability.
What is here instead:
- The filed efficiency, capacity and tank size of both models, side by side below.
- The actual warranty term is printed in each model’s documentation, not in any registry.
Which should you pick?
- Pick the Ruud RTGH-84DVLN-3 if running cost matters most: it uses 6 therms less a year on the same test.
- Pick the RINNAI (RUCS75I) REU-KCM2528FFU-US if the installed price matters more than the running cost: its modeled installed range is $2,122–$3,129 against $2,264–$3,294.
- Neither if you need more than 4.5 GPM at the same time — neither unit lists more. Check how to size a tankless unit by GPM.
Each model on its own
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RINNAI (RUCS75I) REU-KCM2528FFU-US
Its filed figures, class position and running cost on your ZIP.
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Ruud RTGH-84DVLN-3
Its filed figures, class position and running cost on your ZIP.